This application provides evidence that the U.S. Principal and the Senior Foreign Investigator have an established leadership record in participation in the Global Network activities as well as in the design, implementation, and publication of single site and common protocol studies and clinical trials. For the next 5 year cycle, two rigorously-designed randomized clinical trials of antibiotic treatment of infants with suspected serious bacterial infection are proposed. Infection is one of the main causes of death in infants, accounting for about 36% of neonatal mortality worldwide. Current World Health Organization (WHO) recommendations for the treatment of infants with suspected serious bacterial infection include injectable antibiotic therapy but there is limited capacity for intravenous or intramuscular antibiotic administration in many communities in developing countries. Hospitalization of ill infants is not possible frequently because of limited access to hospitals. Injectable antibiotics can be difficult to administer even in some facilities. Furthermore, infection or abscess formation as well as transmission of human immunodeficiency virus, hepatitis, or other pathogens is more common in developing countries. Oral antibiotic regimens have been an effective intervention in older infants and children with pneumonia but not in neonates and young infants with suspected serious bacterial infection. Expert consultants under the direction of WHO have recommended evaluating oral-only antibiotic regimes as alternatives to injectable antibiotics for infants with suspected serious bacterial infection. Thus, there is an urgent need to evaluate the effectiveness of early identification and innovative but simple antibiotic regimens to treat young infants with suspected serious bacterial infection in low and middle income countries. If an oral antibiotic regimen is found to be effective in young infants with suspected serious bacterial infection, antibiotic treatment to young infants with suspected serious bacterial infection may result in an important reduction in neonatal and infant mortality and morbidity worldwide. The proposed team of investigators will work with the NICHD and other sites of the Global Network for Women's and Children's Health Research to design, prioritize, plan, implement, analyze, interpret, and report innovative randomized trials and observational studies that are likely to improve maternal and childhood survival and reduce important morbidities. The qualifications and unequivocal commitment of the U.S. Principal Investigator, the Senior Foreign Investigator, and the team of investigators and staff in Zambia, as well as the full endorsement of the Government of Zambia, the University of Zambia, and the University of Alabama at Birmingham will ensure superior performance if this site is allowed to continue participation in the Global Network.